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In this July 11, 2007, file photo, cars and trucks drive down Interstate 95 in Miami, Florida.

The number of people killed on U.S. roads fell slightly in the first half of 2018, but a top safety organization says it's likely that there will be little change in the number of deaths from 2017 by the end of the year.

The National Safety Council on Wednesday estimated that 18,720 people were killed in traffic crashes from January through June, down about one-half percent from a year ago. Another 2.1 million people were seriously injured during the first half, 1 percent lower than last year.

The council says at the current pace the U.S. could see its third straight year with 40,000 traffic deaths. It says the slight drop in fatalities isn't a sign of progress. It's more of a slowdown from large increases in 2015 and 2016, the steepest two-year rise in over 50 years.

"We aren't making progress, we're treading water," Ken Kolosh, manager of statistics for the council, said in a statement. "We cannot accept 18,000 deaths as the price of mobility."

Fatalities rose 7 percent in 2016, on top of a 7 percent increase from 2014 to 2015, according to the council, which gets its data from states. Prior to 2016, annual deaths had not hit 40,000 since 2007, the year before the economy tanked.

Traffic deaths began dropping in 2008 and reached their lowest point in six decades in 2011 at 32,000.

The council's fatality estimates differ slightly from those of the National Highway Traffic Safety Administration. The government counts only deaths that occur on public roads, while the council includes fatalities that occur in parking lots, driveways and private roads.